AAC .300 AR pistol, trouble shooting question

[GJM]

We are in remote Alaska, 100 miles from town. So tonight, my wife and I go out to zero her new AAC .300 BLK AR pistol, using Barnes factory Vortx ammo. After shot six, the bolt is locked up, out if battery. I had to take a 2x4 off a target stand to beat it open. From that point on, bolt carrier and bolt won't seat forward. Back at the cabin, I disassemble and compare with a Colt 6920 upper. Both bolt carrier assemblies work fine in Colt upper. Neither works in .300 upper. My friend thinks something got loose or out of spec with the barrel extension -- this make sense? Any trouble shooting ideas, other than to send it back to AAC?

[Kokopelli]

It gotta be something along those lines. If the bolt won't lock up with nothing in the chamber, but will in the 6920 upper there's a big clue. What parts and who assembled the 300?

[Iraqgunz]

Since there are feed ramps I would think you can look at the inside of the upper and see if they are mis-aligned with the barrel extension. Look for an obstruction in the chamber area as well. Are there any wear marks around the lugs? Why not try and post some pics?

[GJM]

It is a complete AAC:


http://shop.fortresstactical.com/AAC...03585-sb15.htm

Connectivity is a challenge here, but:

[n517rv]

What buffer and receiver extension are you using? If you take the takedown pin out and push on the buffer does is ride freely in the receiver extension?

Also, has the barrel and chamber been cleaned since new? If not, I would give it a thorough cleaning including using a chamber brush/mop.

[SkyLine1]

GJM stated that it is a stock, new AAC 300blk pistol from the company AAC.

I'm no expert but the gas tube is not looking right to me. Is it crimped at the end? Very hard to tell by the pic. Can you shoot a pic from the rear of the receiver down into the barrel extension?

[DWood]

GJM stated that it is a stock, new AAC 300blk pistol from the company AAC.

I'm no expert but the gas tube is not looking right to me. Is it crimped at the end? Very hard to tell by the pic. Can you shoot a pic from the rear of the receiver down into the barrel extension?

It is hard to tell, but it looks like it is out of round, as if the gas key is striking the end of the gas tube. The tube also looks off center to the left (the upper is upside down in the photo), and the tube looks banged up on the right.

Skyline is right, taking more photos of the tube and the end of gas key will help.

[Iraqgunz]

Lay the upper on that table with the flat top down. Take a picture directly inside towards the gas tube. Preferably straight over the top to see if the tube is tweaked. You can test this yourself by stripping the BCG down to the carrier only and then slowly insert forward. If it doesn't move freely then the tube is out of alignment. Hard to believe that it left the factory this way.

[GJM]

When I stripped the BCG, it won't go all the way forward -- same as when fully assembled. To my ameteur eyes, the gas tube looks off center:

[Iraqgunz]

It is. So you now have two options. Military manual option is to put a large flat tip screwdriver between the wall of the receiver and the gas tube and then tweak it slightly until it appears straight. Then re-test it. 2nd option is to disassemble the upper and re-torque the barrel nut and then re-assemble.

When I stripped the BCG, it won't go all the way forward -- same as when fully assembled. To my ameteur eyes, the gas tube looks off center: